求证明刚才C复杂度或hack

/*
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---
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--------
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    |
    v
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 --
   ---
      --
        ----
            -----
*/
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int n,m,d[200010],cur,b[200010],nxt[200010];
string s,t;
struct node{int l,r;}a[200010];
bool operator<(const node &x,const node &y){
    return x.l<y.l;
}
vector<int>v[200010];
int main()
{
    cin>>n>>m>>s>>t;
    s=' '+s,t=' '+t;
    for(int i=1;i<=m;i++)
        cin>>a[i].l>>a[i].r;
    sort(a+1,a+m+1);
    for(int i=1;i<=n;i++)
        if(s[i]!=t[i])nxt[b[cur]]=i,b[++cur]=i;
    nxt[b[cur]]=1e9;
    for(int i=1;i<=m;i++)
    {
        a[i].l=lower_bound(b+1,b+cur+1,a[i].l)-b;
        a[i].r=upper_bound(b+1,b+cur+1,a[i].r)-b-1;
        if(a[i].l<=a[i].r)v[b[a[i].l]].push_back(b[a[i].r]);
    }
    for(int i=1;i<=n;i++)
    {
        random_shuffle(v[i].begin(),v[i].end());
        sort(v[i].begin(),v[i].end());
        d[i]+=d[i-1];
        for(int j=1;j<v[i].size();j++)
        {
        	int now=nxt[v[i][j-1]];
        	if(now<=v[i][j])v[now].push_back(v[i][j]);
        }
        if(v[i].size()>0)
        {
            char now;
            if(d[i]%2)now=t[i];
            else now=s[i];
            if(now=='0')d[i]++,d[v[i][0]+1]--;
        }
        v[i].clear();
    }
    for(int i=1;i<=n;i++)
        if(d[i]%2)cout<<t[i];
        else cout<<s[i];
    cout<<endl;
    return 0;
}